In the century since BMW’s founding, the company that we know and love has become known for many things. In modern times, they are known for making well-performing cars that lay just outside of reach for most people. They are also known as one of the most distinguished engine manufacturers in the world.
The BMW M10 engine is widely considered to be one of BMW’s most significant engines. It was the engine that ultimately helped BMW lift itself from a post-war slump. It also powered some of BMW’s most iconic road and race cars. Its solid construction and multiple variants made it extremely versatile and durable. The M10 is a testament to BMW engineering and an engine that can be cited as the blueprint for BMW engines for decades to follow.
This article is meant to serve as a comprehensive guide about many aspects of the BMW M10 engine. For that reason, we will break it down into sections so you can skip to whichever part interests you. In this article we will cover the following:
- BMW M10 Engine History
- What Cars Use the BMW M10 Engine?
- BMW M10 Engine Specs
- M10 Performance Mods and Upgrades
- M10 Top End Upgrades
- M10 Cam Upgrades
- M10 Carburetor Upgrades
- M10 Header Upgrades
- M10 Exhaust Upgrades
- Intensive M10 Modifications
- M10 Turbo Upgrades
- M10 ITB Upgrades
- M10 Engine Problems
- Cam Rocker Slippage
- Failure-Prone Thermostat
- Carburetor Issues
- M10 Engine Summary
BMW M10 Engine History
Since 1916, BMW has demanded perfection from their in-house engine design team. Between the engines that they developed for WWI-era fighter planes, to the engines that they manufacture for their road cars, BMW has had a lot of experience in that department.
During the mid-1960s, BMW was looking to up their game in the production vehicle market. They sought to modernize their consumer vehicles, resulting in the creation of the “Neue Klasse” range of production cars. BMW believed that the Neue Klasse range deserved a modern engine to pair with the modern chassis. That belief resulted in the new-for-1962 BMW M10 engine.
The M10 was designed by Baron Alex von Falkenhausen, an engineer and racing driver. He was a disagreeable gentleman with performance on his mind. When BMW demanded that he design a 4-cylinder engine with a 1.3L displacement, he ignored them completely and designed a 1.5L instead. Falkenhausen used his combined engineering and racing knowledge to create the M10. A lesser man with less self-righteousness wouldn’t have likely created something as iconic.
What Cars Use The BMW M10?
Over the course of the M10’s extremely long, 26-year life cycle, the M10 saw quite a few tweaks. BMW developed 13 different M10 variants over that stint and put them in everything from four-door family-haulers to DTM cars.
Since the M10 was used in so many of BMW’s cars between 1962 and 1988, it is a bit tricky to keep all of the variants and power figures straight. To make that mental management a bit easier, here’s a chart:
|M10 Variant||Horsepower / Torque||BMW Models|
|M115||74-80hp / 87lb-ft||1962-64 BMW 1500|
|1975-77 BMW 1502|
|M116||84-103hp / 81-103ft-lbs||1964-1966 BMW 1600— 63 kW (86 PS)|
|1966-1975 BMW 1600-2/1602— 63 kW (86 PS)|
|1967-1968 BMW 1600 ti— 77 kW (105 PS)|
|1975-1980 E21 316|
|1981-1983 E21 315|
|M10B18||98-104hp / 100-107lb-ft||1969-1972 1800— 66 kW (90 PS)|
|1971-1975 1802— 66 kW (90 PS)|
|1980-1983 E21 320i/320is— U.S. only|
|1980-1983 E12 518— South Africa only|
|1982-1987 E30 316 — 66 kW (90 PS)|
|1982-1988 E30 318i— 77 kW (105 PS)|
|1981-1988 E28 518i— 77 kW (105 PS)|
|M118||89-128hp / 106-116lb-ft||1963-1968 1800— 66 kW (90 PS)|
|1963-1966 1800ti— 81 kW (110 PS)|
|1964-1965 1800tiSA— 96 kW (130 PS)|
|1974-1981 E12 518— 66 kW (90 PS)|
|M05||99-118hp / 116-123lb-ft||1965-1970 BMW 2000CS— 88 kW (120 PS)|
|1966-1970 BMW 2000C— 74 kW (100 PS)|
|1966-1972 BMW 2000— 74 kW (100 PS)|
|1966-1971 BMW 2000ti— 88 kW (120 PS)|
|1968-1976 BMW 2002— 74 kW (100 PS)|
|M15||128hp / 131lb-ft||1970-1973 2000tii|
|1972-1974 E12 520i|
|M17||113hp / 122lb-ft||1972-1977 E12 520|
|M43||109hp / 118lb-ft||1975-1979 E21 320|
|1975-1979 E21 320i|
|M64||123hp / 129lb-ft||1975-1978 E21 320i|
|1975-1979 E12 520i|
|M31||168hp / 181lb-ft||1973-1975 2002 turbo|
If there’s one takeaway from that information, it’s that the M10 is a great multi-use engine. The fact that so many different chassis during the Neue Klasse era used the M10 speaks for the engine’s fortitude. The M10’s engineering was so solid that BMW saw no need to replace it for decades. It really is an “if it ain’t broke, don’t fix it” type of situation.
BMW M10 Engine Specs
Although there are multiple variants of the M10 with varying internal specifications, the construction of all M10 variants is similar.
In the same way that covering the M10s applications can be a bit messy, so can covering the specific specifications of the M10. Since there are so many variants, many with different specifications, we’ll cover the specs of each variant in the chart below.
|Engine||M10 and Variants|
|Displacement||91.5 cu in (M115)|
|96.0 cu in (M116, M41, M98)|
|107.8 cu in (M10B18)|
|108.2 cu in (M118)|
|121.4 cu in (M05, M17, M15, M43, M64)|
|121.4 cu in (M31)|
|Aspiration||Naturally Aspirated, Turbocharged (M31)|
|Block Material||Cast Iron|
|Valvetrain||Single Overhead Cam|
|Bore x Stroke||82mm x 71mm (M115)|
|84mm x 71mm (M116, M41, M98)|
|89mm x 71mm (M10B18)|
|84mm x 80mm (M118)|
|89mm x 80mm (M05, M15, M17, M43, M64, M31)|
|Compression Ratio||8.0:1 – 8.8:1 (M115)|
|8.6:1 – 9.5:1 (M116)|
|8.6:1 – 10.0:1 (M10B18)|
|8.6:1 – 10.0:1 (M118)|
|8.5:1 – 9.3:1 (M05, M15, M17, M43, M64)|
As you can see, the M10 comes in many shapes and sizes. Variations to the M10’s displacement, bore, and stroke was made to accommodate different chassis. Typically, the M10 variants with higher displacement were put in longer wheelbase chassis’ to compensate for the additional weight. Later production M10s also tended to have more horsepower as BMW perfected the M10 formula.
Other changes, particularly in respect to compression ratios, also changed dramatically based on the chassis. Sportier M10-powered BMWs typically had higher compression ratios than most civilian-focused M10 chassis. A notable exception is the M31 variant, which had a lower compression ratio to work better with its turbocharger.
M10 Performance Mods and Upgrades
It’s no secret that the M10 is an engine ripe for tuning and upgrades. Even BMW realized the potential of the M10 in the late 70s and early 80s, transforming the piddly 4-cylinder engine into a race-spec beast. All the evidence that you need to prove the M10s competency is the existence of the BMW M12 engine. In 1981, BMW developed the M12 race engine which was built on a standard M10 engine. The M10 block was left in stock form while the rest of the engine received a dramatic engineering overhaul.
The result was one of the most successful engines in racing history. A turbocharged variant of the M12 was used to power the Brabham BT52, which Nelson Piquet drove to victory in the 1983 Formula One World Championship. In qualifying spec, the M12/13 produced 1,400 horsepower, the most power ever produced by a Formula 1 engine to this very day. All based on a BMW M10 engine.
So, obviously, there is a lot of performance that can be extracted from a BMW M10. Even with extensive upgrades, it is nearly impossible to push 1,400hp, but the M10 is still highly receptive to modification.
BMW M10 Top End Upgrades
As we have already covered, the M10 bottom end is the strongest part of the engine. With cast iron construction, the M10 bottom end is able to handle large amounts of horsepower when left alone. With that being said, the M10’s top end is where most of its power potential can be realized.
In recent years, aftermarket support for the M10 has increased by a significant degree. As the BMW 2002 and E21 chassis have become more desirable, aftermarket manufacturers and tuning companies have recognized the growing desire for better M10 support. At this point, most aftermarket support comes in the form of engine refresh components rather than performance components.
As most M10 engines are nearing their 60th birthday, many stock M10s have degraded significantly since they rolled off of the assembly line. As a result, simple engine refresh modifications are enough to make a significant increase in M10 performance.
BMW M10 Cam Upgrade
One of the most significant performance-boosting mods for a BMW M10 is a pair of upgraded cams. Due to the simplicity of the M10 engine, upgrading internal mechanical parts has a huge effect on performance. The camshaft profile that you choose to run is a great example of this.
Schrick is a household name to performance BMW enthusiasts and the primary supplier of upgraded M10 cams. The beauty of upgrading to Schrick cams is the amount of customizability that you are able to achieve in regard to cam profiles. Schrick manufactures M10 cams with six different grinds to suit your personalized needs.
Typically, lower degree cams are more suited for M10s destined for street duty. Schrick makes 284 and 292-degree grind cams for higher performance intake and exhaust durations without sacrificing much streetability. The higher the degree grind, the more high RPM performance can be extracted from an M10. This usually comes at the cost of low-rpm torque and horsepower delivery. With a Schrick low-degree grind cam upgrade, a significant bump in mid-range torque and power will be immediately noticeable.
Schrick also manufactures race-spec M10 cams for those looking to gain heaps of power at high RPMs. Their 304, 316, 328, and 336-degree grind cams are purpose-built for M10 racing applications, not suited for street use. These high-performance cams are built to be used in conjunction with other high-performance M10 modifications. These mods include side-draft carburetors and an upgraded fuel system.
M10 Cam Upgrade Considerations
Upgrading your M10 cams is one of the best ways to boost horsepower and torque figures. It is also important to note that upgraded cams are a prerequisite for most of the M10 mods that follow on this list. There are a few notable considerations that need to be considered when upgrading your M10 cams as well.
If you are considering upgrading your M10 cams, you’ll have to pay close attention to the compression ratio of your given M10 engine. The compression ratio of your M10 will determine which upgraded cam is best for your application. Typically, higher compression M10s can handle a more significant cam degree grind without sacrificing too much low-end performance. If you select an upgraded cam that is too aggressive for your M10, your car will become undrivable at low speeds.
It is also important to remember that a tune will be required to reap the highest benefits from upgraded M10 cams. Without a tune, the stock M10 ECU won’t recognize the difference in intake and exhaust duration.
Upgrading your M10 cams also has a major effect on most other M10 performance modifications. When upgrading other components, like the fuel system or carburetors, an upgraded camshaft needs to be factored into additional upgrade decisions.
BMW M10 Carburetor Upgrade
As the M10 was developed before fuel injection was widely used, it employed carburetors for its air/fueling needs. Most M10 aficionados agree that the factory Pierburg 2BE carburetor is inferior to many aftermarket options.
Carburetors are a very sophisticated piece of engineering. Their intricacies are too numerous to go into detail here, so we won’t put you to sleep by explaining them. However, it is important to explain why an upgraded carburetor will increase the performance of an M10 engine.
As with all carbureted engines, the M10 relies on carburetors to supply an appropriate air/fuel mixture to the intake. Not all carburetors are created equal, with some having inadequate jet sizes, small venturi bores, or incorrect choke styles for a specific application.
As the air/fuel mixture that enters the engine is one of the most important aspects of an internal combustion engine, the efficiency of a carburetor for engines without electronic fuel injection is integral to engine performance. For that reason, upgraded carburetors are one of the most effective performance mods for an M10 engine.
In the M10 community, the most popular upgrade choice is the 32/36 Weber carburetor. The 32/36 Weber upgrade is far more efficient and effective than the stock Pierburg M10 carbs. The resulting benefit is a net 18% increase in horsepower and 10-20% better fuel economy. That’s a difference that you’ll feel immediately.
Another benefit to a 32/36 Weber carb upgrade is that it is a simple bolt-on modification. Multiple sources sell the Weber upgrade kit with all of the necessary bits to get you going right out of the box. The upgraded carb bolts up directly to the M10’s 2-barrel manifold and uses the factory coolant plumbing.
In most cases, the 32/36 Weber carburetor should yield the above benefits without any fiddling. However, you can tune the carburetor if you seek a different air/fuel ratio for your M10 application.
BMW M10 Header Upgrade
Exhaust system upgrades are another way to source a bit more power for your M10 engine. Most M10 powered BMWs made after 1974 have a highly restrictive exhaust manifold that dissipates heat poorly. For that reason, most M10 enthusiasts recommend purchasing aftermarket headers with higher flow and better heat management.
The most common M10 header upgrade is with the higher-flow Tii M10 exhaust manifold. As the Tii manifold is less restrictive and has better heat management properties, an estimated 4-6% increase in horsepower and torque can be expected from the upgrade. To achieve maximum performance from an upgraded Tii manifold, the ECU needs to be tuned to reflect the upgrade.
In recent years, Tii headers have become increasingly difficult to find. Since the M10 is over a half-century old, finding one in good condition is like stumbling upon a unicorn. For that reason, many M10 enthusiasts have turned to other aftermarket header options.
The most widely used alternative to the Tii headers is the Ireland Engineering shorty M10 header kit. Ireland Engineering is arguably the most reputable aftermarket manufacturer for 2002 parts. They have a stellar reputation for providing quality products and their M10 headers are no exception. The IE shorty headers also feature a few key benefits over the Tii header option.
The IE M10 headers are the most effective option in terms of heat management. They can be purchased with ceramic coating, further reducing under hood temperatures. Their stainless steel construction guarantees strength, which is further compounded by beefy ⅜” flanges.
M10 enthusiasts that have gone the IE route have noted that the shorty headers provide an even more substantial boost in performance over the Tii headers. A 2002 enthusiast forum member dyno tested the IE headers against Tii headers with impressive results. Overall, the IE M10 headers edged out the Tii headers by over 8hp and 8lb-ft of torque. That is a whopping 10-15% power increase over the stock manifold.
M10 Exhaust Upgrades
While upgrading just the M10 headers will yield an impressive increase in performance, pairing a header upgrade with an upgraded exhaust system will make an even bigger difference. Conversely, if you only upgrade your M10 exhaust system without upgrading your headers, there will be a noticeable increase in power but not as much as a header/exhaust combo.
The factory 1 5/7” M10 exhaust is noticeably restrictive and not designed with high performance in mind. A quality aftermarket exhaust will allow for the M10 engine to expel exhaust gasses more efficiently and reduce backpressure.
Unlike most of the other M10 mods on this list that are limited in terms of aftermarket options, there are quite a few aftermarket M10 exhaust choices. Among the most common manufacturers are Supersprint, Sebring Reproduction, Ireland Engineering, and Eisenmann.
Like the header upgrade, Ireland Engineering is your best bet when it comes to upgrading your M10 exhaust. The IE 2” stainless steel exhaust system is the best bang for your buck as far as quality and performance are concerned. Ireland Engineering sells their 2” M10 exhaust for both pre and post 1974 vehicles, so make sure that you order the correct one if you decide to pull the trigger.
The other obvious benefit of an upgraded exhaust is a better exhaust note. Ireland Engineering notes that while the 2” stainless exhaust will be a bit louder than stock, the exhaust note will be crisp, not ‘ricey.’ While it won’t set off any car alarms, it’s certain to break some necks as you drive by.
Intensive M10 Engine Upgrades
Up to this point, we have covered M10 upgrades that can be done without too much fuss. If combined, the upgrades listed above should produce an M10 capable of 150-200 horsepower at the wheels. That’s a pretty significant jump over factory power and a difference that’ll be enough for most people.
If you are looking for more power than that, upgrades start to become much more expensive and involved. Due to the complexity of the modifications beyond this point, we won’t cover them in great detail here. Websites like bmw2002faq.com and bimmerforums.com are great resources to connect with M10 experts who have extensive and detailed knowledge when it comes to building race-spec M10 behemoths. With that being said, we will briefly discuss some of the more significant modifications needed to get an M10 to a 200whp power goal.
BMW M10 Turbo Upgrade
Of course, one of the most obvious ways to up the power of an M10 is to introduce forced induction. As we covered before, the M10 is a very strong and capable engine for turbocharging. The cast-iron block is good for up to 10psi with factory internals, given they are in good condition.
One of the most significant upgrades that would be needed before a turbo is a fuel system overhaul. Most people opt for a k-jet style system of injection, which is sufficient for turbocharging. A management system, like a MegaSquirt, is needed to tell the ECU how to handle the new equipment. Ignition timing would need to be sorted as well.
From there, all of the standard and necessary turbo equipment would need to be sourced. This generally includes the turbo itself, wastegate, charge pipes, flanges, head bolts, etc. This excludes the custom fabrication work required for all of these parts to work in unison. Additionally, the wiring harness would need to be modified, along with oil feed lines and coolant supply lines.
Of course, with the additional power comes the need to upgrade other aspects of your M10 powered-car. The suspension and brakes would need to be upgraded to handle the extra power. A stiffer clutch and other transmission-related modifications would be needed as well.
Turbocharging a BMW M10 is a very extensive job, the same as turbocharging any other N/A motor. Some might argue that it is more difficult than turbocharging other N/A engines due to the M10s age and antiquated components. It really depends on how deep you are looking to go down the rabbit hole.
Turbocharging an M10 is certainly possible, and many people have done it. However, most people agree that it is one of the least economical ways of producing a lot of power from an M10 chassis.
BMW M10 Independent Throttle Bodies
Another modification reserved primarily for race-spec M10s is an upgrade to independent throttle bodies. Independent throttle bodies, or ITBs, are an upgrade centered around improving throttle response and increasing airflow to the engine.
Due to the fact that individual throttle bodies are extremely expensive and highly specialized, they are typically meant for meticulously tuned performance engines that become bottlenecked by standard intake systems. For that reason, they are typically a finishing touch rather than a starting point.
The same principle can be applied to an M10 engine. If you have performed all of the engine upgrades listed above and are looking to round out a performance M10 build, ITBs are a great finale. With an ITB setup, air rests in the intake plenum and is pulled directly into the engine with no delay. This crispens throttle response time.
Upgrading to ITBs is no easy task as far as M10s are concerned. The stock fuel system will have to be upgraded to an injected system and an engine management system is required. ITBs will also significantly increase the noise generated by your engine, making it impractical for street use.
BMW M10 Engine Problems
To be blunt, this section will be brief. The BMW M10 engine is a highly praised engine by many enthusiasts, its reliability being one of its most widely cited attributes. While the M10 is known for being a truly bulletproof engine, its age is its main downfall.
Most M10s are over 30 years old at this point. Age is the ultimate force that works against even the best engines. However, if an M10 is maintained properly and regularly serviced, it is unlikely to have any major issues.
Common M10 Engine Problems
In the decades that the M10 has been in service, there is very little information available in terms of common issues or weak spots with the engine. That is likely because there aren’t many of note. The situation is the same with most old BMW engines. Due to the fact that they had relatively few moving parts or electrical components, there weren’t many things that could go wrong. However, there are a few noted M10 engine issues, most of which are uncommon or not serious. Here are the main M10 issues:
- Cam Rocker Slippage
- Failure-Prone Thermostat
- Carburetor Issues
Cam Rocker Slippage
M10 cam rocker slippage is perhaps the most commonly cited problem for aging M10s. As engines age, their internal components aren’t able to withstand the same stressors as new ones. In the M10, this often manifests with problems with the cam rockers.
Under normal driving loads, it is unlikely that an M10 will experience any rocker issues. Problems with the cam rockers typically only begin when sustained high-revs are introduced. In other words, cam rocker issues begin when an M10 is pushed to its limits for an extended period.
At high revs, the cam rockers can slip sideways. In most cases, the tip of the rocker arm slips between the valve stem, causing the retainer to crack in half. The most common fix for this problem is installing more rigid retainers, which prevent the rocker arms from slipping.
A failing thermostat is another common M10 issue that has everything to do with the engine’s age. The M10s thermostat is one of the most brittle and failure-prone components on the engine. Adding age to an already iffy part is a recipe for problems.
Even in factory form, the M10s thermostat was noted as a problem area for the engine. BMW did not take their time in manufacturing a high-quality unit for the M10 from the beginning. M10 thermostats are known to open too early, too late, or fail completely in the shut position. This is a severe issue as a stuck thermostat can cause serious overheating issues. A stuck thermostat has the potential to cause terminal head gasket or cylinder head issues.
For that reason, BMW recommends that you always keep an eye on your M10-chassis’ temperature gauge, making sure that the vehicle isn’t overheating. It is also recommended to change your M10 thermostat every 30,000 miles to prevent any headaches down the line.
The only other significant M10 problem to note is high-mileage carburetor issues. As we discussed earlier, carburetors are extremely complex parts with a ton of internal components. When carburetors age, many of their internal parts become worn or clogged from years of cycling air and fuel into the engine.
Typically, carburetors need to be assessed and re-tuned, if not replaced, every 90,000 miles. Any more mileage than that and you might start to encounter intermittent running issues and dreadful fuel economy. The factory Pierburg 2BE carburetor is known to be problematic and inefficient. If you do encounter any carburetor issues with the stock Pierburg, it might be worth investing in a Weber carb upgrade. Not only will it allow your M10 to perform at a much higher degree, but it’ll also improve gas mileage dramatically.
M10 Engine Summary
The BMW M10 engine is arguably the most important engine in BMW’s entire catalog. Following WWII, the M10 allowed BMW to climb out of their financial slump by powering the first generation of modern BMW production cars.
The M10 is beloved for quite a few reasons, the legendary chassis’ that the 4-cylinder powered is one of them. From the 2002 to the E21, the E9 and the E12, the M10 was the powerhouse for some of BMW’s most beautiful and successful creations.
Not to mention, the M10 is an engine with huge amounts of performance potential. Modified M10s have been used in many of BMW’s early race cars, proving its performance pedigree. That performance potential extends to street use as well, with aftermarket support for the M10 blossoming in recent years. The love for the M10 in the BMW community has made modification information easy to track down. If you have a specific goal for an M10, chances are it has already been done and cataloged meticulously.
A lot of fan support for the M10 comes from its unwavering reliability and strength. Due to the M10s simplicity, there isn’t a ton that can go wrong with it. That, paired with its solid cast-iron block and aluminum head, a well-maintained M10 will likely outlive most people.
The BMW M10 is a legend, there’s no arguing with that. Whether you are looking to turn your BMW 2002 into a period-correct track monster or spruce up an M10-powered E21 daily driver, the M10 isn’t likely to let you down.
If you enjoyed reading about the BMW M10 engine, check out some of our other BMW engine content. For more classic BMW content, check out our BMW E30 Engine Swap Guide. As always, safe driving!